I want to do an OW course next week. Will be in Bangkok and happy to fly anywhere in the region -- sounds like Vietnam is cheapest, but it it as beautiful as elsewhere? Where would you all recommend, taking into account season/weather and cost? I'm not into the backpacker beach town vibe, somewhere more laid-back would be more my scene :)

I wouldn't say the diving in Vietnam is especially good, visibility tends to be poor. Taking into account weather, season and cost, why not consider staying in Thailand? Diving is pretty good there. A lot of people do OW on Ko Tao, but if you don't want the backpacker scene, then maybe don't go there. You might prefer to learn in Krabi, Ko Phi Phi, Phuket or Ko Lanta on the west coast. Courses should still be pretty cheap. Elsewhere in the region, you could consider learning in the Philippines, say somewhere like Puerto Galera.